Fair weather nocturnal inland wind surges and atmospheric bores: Part I Nocturnal wind surges

Available Australian data are examined for evidence of nocturnal wind surges arising from sea-breeze activity. The data show conclusively that warm season sea-breezes frequently give rise to afternoon and evening surges, many persisting until 2200-2400 hr local time, and penetrating 200 to 300 km inland. In low latitudes 400 km or more may be attained. The presence of an escarpment near the coast does not hinder the formation of a surge further inland, the surge behaving much as it would have done over featureless terrain. Apart from heating, the most important factor determining inland penetration is the ambient wind. So long as this is modest (5 m s-') surges can still form, but they are considerably affected in depth and speed of propagation, and place and time of development. The magnitude of the Coriolis parameter is probably also a factor determining penetration, which is greater in low latitudes. A heated peninsula, with a coast-normal ambient wind, may produce a convergence of sea-breeze surges near one coast. Observations on Cape York Peninsula show that the stronger surge often continues to propagate in a modified form (as a bore) over the sea for great distances. Nocturnal surges, at least partly dependent on strong diurnal heating in the neighborhood of synoptic scale troughs, may also become bore-like in character, and these are briefly examined.